Various systems for the injection of fuel under pressure into the induction air flow through the intake manifold of an engine are well known in the art. In one such system, as presently used in certain commercially available passenger vehicles, and as disclosed, for example, in U.S. Pat. No. 3,680,535, entitled "Fuel Injection System for Combustion Engines" issued Aug. 1, 1972 to Konrad Eckert, Heinrich Knapp, Reinhard Schwartz and Gregor Schuster, the continuous port injection of fuel under pressure is mechanically controlled by means of an air sensor controlling fuel flow to the engine, a throttle valve in a separate throttle body being used to control air flow to the engine.
In another such system, fuel, as controlled either mechanically or electrically, is injected under pressure into a common induction passage so that the resulting air-fuel mixture can be applied by the intake manifold to all cylinders of the engine. This latter type system which is a type of pressure carburetor may also be referred to as a throttle body injection system.